Secondary batteries capable of charging and discharging are being widely used as an energy source of wireless mobile devices. Further, secondary batteries are gathering attention as a power source of electric vehicles (EVs), hybrid electric vehicles (HEVs) and the like that are being presented as a measure to solve air pollution and the like of conventional gasoline vehicles, diesel vehicles and the like that use fossil fuels.
In medium to large scale devices such as vehicles and the like, due to the necessity of high power and massive storage capacity, a battery module where a plurality of batteries are electrically connected and a medium to large scale battery pack including the battery module as a unit module are used. Since it is desirable to prepare such a battery module and a battery pack in as small size and weight as possible, a prismatic battery, a pouch-type battery and the like that may be stacked in high density and high capacity to weight ratio are mainly used as a unit battery of a battery module. Especially, the pouch-type battery that uses an aluminum laminate sheet and the like as its exterior material is gathering attention due to the advantage that it has a small weight and has low manufacturing costs and that it is easy to transform the shape.
Batteries that constitute a battery module generate massive amount of heat in a charging and discharging process. Especially, since the aluminum laminate sheet of the pouch-type battery that is widely used in battery modules and battery packs of high power and massive storage capacity has a surface that is coated with a polymer material having low conductivity, it is to difficult to effectively cool the temperature of the entire battery. Unless the heat of the battery module generated in the charging and discharging process is removed effectively, heat accumulation occurs, which may consequently promote deterioration of the battery module, and in some cases cause ignition or explosion. Therefore, the battery module of high power and massive storage capacity and the battery pack where the battery module is mounted definitely need a means for cooling the batteries embedded therein.
A battery module is generally prepared by a method of stacking a plurality of batteries in high density, and the adjacent batteries are stacked to be spaced apart from one another so as to remove the heat generated during charging and discharging. For example, without using a separate member, the batteries themselves may be sequentially stacked to be spaced apart from one another by a certain distance, or in the case of batteries with low mechanical rigidity, they may be embedded in a cartridge and the like in combinations of one or two or more batteries, and a plurality of such cartridges may be stacked to form the battery module. Between the stacked batteries or battery modules, a passage of a refrigerant such as cooling water may be provided, or a cooling plate (heat sink) or a cooling sheet may be utilized so that the heat being accumulated may be effectively removed.
Most of such conventional means for cooling structures involve cooling heat by interface contact with air such as thermal conduction of an interlayer heat conductor or increase of convection effect and the like by expansion of surface area, and has a problem that the heat release effect significantly deteriorates in a closed space. Especially, devices configured to emit heat such as conventional heat sink and the like use conduction or the convection phenomenon to emit heat, and are generally made of metal material having excellent heat conductivity in order to enhance such effects. However, since a method based on heat transfer is affected by the latent heat of the medium transferring heat and the speed of the heat transfer, there are limitations.
As the capacity increases, due to high integration, an increased amount of heat may be generated, and thus there is a need for a battery module that may be prepared in a simple and compact structure while providing high power and massive storage capacity, and that has excellent life expectancy properties and safety due to a high cooling efficiency.